Fluid transporting conduits, such as pipes or tubes, are widely used in many different industries and applications, and are often insulated to help maintain a desired temperature of the medium that is being transported. Industrial conduits, such as those used in the chemical, petrochemical, power, pump, and refinery fields are usually located outdoors and must be protected from water and other environmental factors. The penetration of liquid, such as water, precipitation, or moisture from the air into an insulation system can cause loss of insulating performance, damage to the insulation, or corrosion of the conduits. The loss of insulation property can also affect the contents of the conduit. For example, a vapor component of the conduit's contents may become condensed, i.e., the liquid transported by the conduit may freeze and disrupt the fluid flow within the conduit or rupture the conduit. This partially frozen liquid may also be transported through the conduit into processing equipment and adversely affect the operation of the equipment.
To prevent damage to the insulation, a jacket is usually applied around an insulated conduit to keep environmental factors from contacting the insulation. These jackets can be made of metal, such as aluminum and stainless steel, flexible or semi-rigid materials, such as thermoplastics, or any other suitable material. It is relatively easy to install water resistant jackets to straight lengths of insulated conduits by placing the overlap that forms the jacket's seal in a watershed position in order to direct water away from the area of the overlap. However, installing jackets, especially metal jackets, on fittings having angled elbows or T-configurations in a water resistant fashion has been problematic. It is difficult to conform the shape of the jacket to angled fittings covered with insulation because of the varying diameters of the pipe and the insulation covering the pipe. In practice, it is economically disadvantageous to produce pre-shaped jackets for covering pipes of various sizes having insulation of different thicknesses.
In order to address this problem, it has been known to form adjustable jackets having overlapping connecting flanges formed with inter-engageable ribs and grooves or pleats. For example, known adjustable jackets include a sliding and adjustable seal along the longitudinal edges of two semicircular pieces that join to form a jacket over a pipe bend or a straight length of pipe. Each of these semicircular pieces has a flange along its longitudinal edge designed to overlap with the flange of the opposing semicircular piece when both are placed around a pipe bend. The overlapping flanges are positioned so that the semicircular piece on the inside (contacting the insulation in the area of the overlap) is first positioned while the outside piece is then positioned onto the pipe so that the amount of overlap of the longitudinal edges of the outside piece with respect to the longitudinal edges of the inside piece can be increased or decreased in order to tighten or loosen the overall fit of the combined jacket onto the pipe bend. Each of the longitudinal edges of the inside piece has a semicircular raised ridge that faces the outside piece and runs longitudinally along the length of the flange. Each of the longitudinal edges of the outside piece is correspondingly shaped to include a tab formed by a flat strip of jacketing along the longitudinal edge that is slightly depressed with respect to the rest of the jacket. When the inside and outside pieces are properly positioned, the raised ridge of the inside piece rests on the conduit while the tab of the outside piece overlaps the raised ridge and rests flat against the outer surface of the inside piece.
While such known adjustable jackets are designed to be easily installable around pipe bends and to inhibit water or other moisture from entering the underlying insulation, it has been recognized that water or other environmental factors are able to breach the seals provided by the outer tab and the inside ridge. It is believed that this previous design can promote the entry of water or other environmental factors into the seam by creating unfavorable interfacial forces between water and the inside and outside pieces of the jacket. It is believed that the area in which the outside tab contacts the outer surface of the inside piece, which was designed to provide a first seal and primary barrier to water or moisture entry, facilitates the entry of liquid into the seam through a capillary effect. When in contact with liquid, the flat overlapping orientation of the outside tab with respect to the outer surface of the inside piece can provide boundary conditions between the outer edge of the seam and liquid droplets that favor formation of capillary pressure and subsequent capillary action, known as wicking. It is possible that the orientation of the outside tab increases the adhesive forces between the solid jacket and the liquid molecules. When these adhesive forces overcome the cohesive forces in a liquid droplet, which are provided, for example, by the intra-molecular forces between water molecules, the liquid droplet spreads across the surface in a process known as wetting. This increases the surface area of the interface between the liquid and the jacket, and subsequently increases the overall adhesive forces between the liquid and the solid jacket.
Once capillary pressure is formed between the outside tab and the outer surface of the inside piece, the capillary continues to draw in more liquid if a constant supply of new droplets are in contact with the boundary interface. This is likely in conditions such as a rainstorm. The liquid that accumulates in the area between the inside ridge and the outside tab then interfaces with the second seal provided by the contact between the top of the inside ridge and the inner surface of the outside piece. As the surface of the semi-circular ridge approaches the inner surface of the outer piece, the two solid surfaces approach a parallel orientation, which, in the presence of liquid, provides increased surface area and thus increased adhesive forces between the solid surfaces and the liquid. These conditions facilitate movement of the liquid beyond the seal by capillary action. Once this second seal is breached, the liquid can contact the insulation surrounding the conduit.
The insulation itself can also act as a strong wicking agent that facilitates further entrance of liquid inside the jacket. Furthermore, the low contact angles between the liquid and solid surfaces of the jacket, such as water that gathers in the area between the outside tab and the inside ridge, provides capillary adhesion in which water sticks between the two surfaces and draws them together. Therefore, even when a liquid is not being introduced to the boundary surfaces of the jacket, water or moisture from a previous rainstorm or condensation can be present in areas such as between the outside tab and the inside ridge. Although there may be no capillary motion, the trapped liquid can “prime” the interfacial forces for capillary action upon future contact with a liquid. This effect increases the likelihood of liquid breaching the seals through capillary action.
A need exists for an adjustable jacket that is easy to install, can be arranged around pipe bends, and prevents entry of liquid, such as water, moisture, and other environmental factors from entering the jacket, especially through capillary effects.